The diagram above shows inductive loop detectors often used at intersections to detect traffic and trigger and green light. Black shows you the shape of the cuts to look for in the pavement; yellow highlights where to place your rims. Yes, it’s ridiculous that a study in electrical engineering is required just to cross the street.

The induced loop detectors used 30 years ago are still commonplace today, but newer (and more expensive) technology is available. I’ve reported before on radar, ultrasonic, and video detectors that are specifically tuned for bicycles.

Video detection works well in California, but it’s not always the panacea often touted by cycling advocates. Video detectors are easily identifiable by the cylindrical camera housings mounted somewhere high above the intersection. If you have trouble triggering even video detectors, Steve in DFW explains their operation and provides good pointers. He notes, for example, that the road edge can often be beyond the field of view of the video camera. If you’re in the shoulder, the camera doesn’t see you. They also can’t see ninja cyclists operating their invisible bikes at night without lights. Again, special knowledge is sometimes required to cross the street.

You might remember Iteris and their SmartCycle bicycle detection system. All new video detection systems from Iteris come with the SmartCycle system installed, and SmartCycle is available as a free firmware upgrade on installed systems. This video explains how the system works.

Transportation planners often hesitate to lengthen the traffic signal green phase for cyclists because it messes up their traffic flow projections and intersection Level of Service for cars. This bike detection allows signals to increase this green phase time only when bikes trigger the green light, completely eliminating LOS as an excuse to change the timing.

Because multiple vendors now offer bicycle detection capabilities that change the green phase timing just for bikes, cycling advocates really should bug your local transportation departments to enable these capabilities in their traffic lights.

“A third grant application submitted directly to MTC under their Climate Initiative Innovative Grant Program was approved for funding by the MTC on October 27, 2010. The funds will be allocated to the City in Spring 2011.
Innovative Bicycle Detection System Proiect: This project will test and evaluate eight different technologies that allow bicyclists to be detected by traffic signals so they can receive a green light. Testing will occur on the San Fernando Street, and Williams Street/Bollinger Road bicycle corridors in 2012. Once a “best” technology is identified, this project will implement the technology on additional corridors in San Jose’s Primary Bikeway Network. The grant project will be completed by December 31, 2013″